As a vehicle decelerates to a stop whilst traversing terrain having a deformable, low-mu surface (e.g., sand, gravel, mud, or wet grass), the wheels of the vehicle may dig or sink into the soft surface of the terrain due, at least in part, to the brake torque and drag torque respectively applied to the wheels by the vehicle brake system and the surface of the terrain. The digging or sinking of at least certain of the vehicle wheels may be compounded or made worse in an instance wherein the vehicle is decelerating to a stop as it travels across a side slope (also referred to herein as “slope” or “gradient”) having a deformable, low-mu surface. More particularly, as vehicle travels across a side slope, the weight of the vehicle is transferred to the “downhill” side of the vehicle. This weight transfer and the effect of gravity results in an increased vertical force being applied to the downhill side of the vehicle which may cause the wheels on that side of the vehicle (i.e., the “downhill wheels”) to dig or sink further into the surface than those on the “uphill” side (i.e., “uphill wheels”). Additionally, in an instance where the vehicle has larger brake device components fitted to the front axle of the vehicle, the front axle may have a greater brake or negative torque applied thereto as compared to the rear axle. As such, while both the front and rear downhill wheels may dig or sink significantly into the surface, the front downhill wheel may dig or sink further than the rear downhill wheel.
The digging or sinking of the wheels of the vehicle may have a number of potentially adverse effects. For example, the digging or sinking of the downhill wheels of the vehicle may cause the vehicle to experience increased lateral movement and/or the vehicle may experience increased roll or roll rate in the downhill direction. In an instance where the front wheels dig or sink into the surface more than the rear wheels, the rear wheels may slide or drop sideways down the slope due to the soft surface and gravity. Further, as the vehicle wheels dig or sink into the surface, a substantial amount of material forming the surface may build-up around the downhill vehicle wheels. This build-up of surface material may make it more difficult to subsequently pull away in a composed manner since the vehicle must first overcome the build-up of material before progressing as desired (i.e., the vehicle wheels have to rise up through the material to a point where the tire(s)is/are on top of or at least relatively close to the surface before progressing). This may result in greater lateral movement of the vehicle and ultimately lead to the vehicle having to travel down the slope in order to gain enough momentum to progress across the slope.
Accordingly, it is an aim of the present invention to address, for example, the disadvantages identified above.